Tracking of and communication with mobile terminals using a battery-powered wireless network infrastructure

ABSTRACT

There is provided a method of reducing energy consumption of tag readers in a wireless network, the method comprising: (a) turning a transmitter and a receiver of the tag reader to a power-off state; b) powering-on the transmitter of the tag reader for a limited transmission time frame; c) during the transmission time frame, transmitting a beacon message comprising an identifier of the tag reader, channel characteristics of the tag reader and a powering-on schedule of the receiver of the tag reader, for allowing tags in the network to communicate with the tag reader, where the tags are almost continuously in a power-on state; d) powering-on the receiver of the tag reader during a limited reception time frame in accordance with the schedule, for enabling the receiver to receive messages transmitted by the tags in the network if required; e) repeating steps a) to d) periodically. There is further provided a battery-powered tag reader which reduces energy consumption. There is further provided a battery-powered wireless network with an energy management for tag reader. There is further provided a method of increasing probability of detection of rapidly moving clusters of mobile nodes in a wireless network.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present patent application claims the benefits of priority ofCanadian Patent Application No. 2,559,471, filed on Aug. 31, 2007, atthe Canadian Intellectual Property Office and entitled: “Undergroundcommunication network system for personal tracking and HVAC control”.

FIELD OF THE INVENTION

The present invention generally relates to the field of wirelesstelecommunication networks. The invention more particularly concernsTracking of and Communication with Mobile Terminals using aBattery-Powered Wireless Network Infrastructure.

BACKGROUND OF THE INVENTION

With the advent of the Internet and the ever increasing miniaturizationand integration of electronic circuits, new possibilities have begun toemerge in the field of data communication networks.

Several applications, such as industrial automation and monitoring,localization of personal and assets, and defense and securitymanagement, have specific requirements that cannot be met with wirednetworks or existing wireless networks.

In order to provide a solution for these types of applications,significant new research has been conducted in the past ten years todevelop new and more efficient wireless network systems and protocols.

This research has resulted in the appearance of a plethora ofproprietary and non-proprietary wireless networking technologies. Some,such as WLAN (IEEE 802.11), WiMAX (IEEE 802.16), Bluetooth (IEEE802.15.1), ZigBee (IEEE 802.15) and the upcoming SP100 protocol arestandard non-proprietary wireless networking protocols. Standardnetworking technologies generally involve trade-offs between numerouscompeting issues (scalability, topology, energy consumption, range,frequency, etc.). They are therefore difficult to adequately tailor tothe specific needs of particular applications. This invention, incontrast, does not operate on a standard and can be tailored with a highdegree of specificity to particular applications. This invention is alsodifferent from other proprietary network protocols, such as the TSMPfrom Dust Networks and the SensiNet® from Sensicast, two othernon-standard wireless networking protocols.

Beacon-based networks have been implemented in some cases. While thesenetworks have facilitated some useful advances, they either only operatein star configurations or consume too much energy to be battery-powered.Many applications mandate a mesh network that is highly scalable, interms of the maximum number of hops and node density for which thenetwork remains reliable. Many applications also require a networkconnection time in the order of seconds. Mesh network techniques thatrely on central synchronization cannot meet these demands.

Ad hoc communication in mesh networks usually implies local allocationof communication resources without a central host. Low energyconsumption must prevail in allocating these resources.

Real-time tracking of mobile terminals in underground or confinedenvironments (e.g. underground mines, navy vessels) is challengingbecause: (1) Mobile terminals cannot receive satellite or cellularsignals from Wide Area Networks (WAN) [e.g. GPS does not work]; (2)Deploying Local Area Network (LAN) infrastructure is prohibitivelyexpensive, operationally impractical and/or unreliable because (a) RFsignal propagation is non-line-of-sight and confined to tunnels,corridors or rooms with waveguide constraints; (b) Power outlets arescarce and installing additional power wiring, connectors and adaptersis a tedious undertaking; (c) Many sites are in remote areas and/or indeveloping countries where skilled labor for installation andmaintenance of telecom networks are in short supply; (d) Wiring is proneto damage.

From the foregoing, it appears that there is a need for a novel wirelessnetwork technology which obviates the above-mentioned drawbacks.

SUMMARY OF THE INVENTION

As a first aspect of the invention, there is provided a method ofreducing energy consumption of tag readers in a wireless network, themethod comprising:

-   -   a) turning a transmitter and a receiver of the tag reader to a        power-off state;    -   b) powering-on the transmitter of the tag reader for a limited        transmission time frame;    -   c) during the transmission time frame, transmitting a beacon        message comprising an identifier of the tag reader, channel        characteristics of the tag reader and a powering-on schedule of        the receiver of the tag reader, for allowing tags in the network        to communicate with the tag reader, where the tags are almost        continuously in a power-on state;    -   c) powering-on the receiver of the tag reader during a limited        reception time frame in accordance with the schedule, for        enabling the receiver to receive messages transmitted by the        tags in the network if required;    -   d) repeating steps a) to d) periodically.

As a further aspect of the invention, there is provided a tag reader ina wireless network comprising:

-   -   a transmitter;    -   a receiver;    -   a processing unit configured to turn a transmitter and a        receiver of the tag reader to a power-off state, to power-on the        transmitter of the tag reader for a limited transmission time        frame, to transmit, during the transmission time frame, a beacon        message comprising an identifier of the tag reader, channel        characteristics of the tag reader and a powering-on schedule of        the receiver of the tag reader for allowing tags in the network        to communicate with the tag reader, and to power-on the receiver        of the tag reader during a limited reception time frame in        accordance with the schedule for enabling the receiver to        receive messages transmitted by tags in the network if required.

As another aspect of the invention, there is provided a wireless networkcomprising a plurality of tags and a plurality of tag readers, where tagreaders are configured to be continuously in a power-off state exceptduring prescheduled reception and transmission time frames, and wheretags are configured to be almost continuously in a power-on state, wherethe tags and tag readers exchange messages therebetween in order foreach tag to be connected to one tag reader in the network.

As another aspect of the invention, there is provided acomputer-readable medium containing instructions for controlling atleast one processor to perform a method of reducing energy consumptionin an immobile node in a wireless network, the method comprising:

-   -   a) turning a transmitter and a receiver of the tag reader to a        power-off state;    -   b) powering-on the transmitter of the tag reader for a limited        transmission time frame;    -   c) during the transmission time frame, transmitting a beacon        message comprising an identifier of the tag reader, channel        characteristics of the tag reader and a powering-on schedule of        the receiver of the tag reader, for allowing tags in the network        to communicate with the tag reader, where the tags are almost        continuously in a power-on state;    -   c) powering-on the receiver of the tag reader during a limited        reception time frame in accordance with the schedule, for        enabling the receiver to receive messages transmitted by the        tags in the network if required;    -   d) repeating steps a) to d) periodically.

Preferably, the wireless network comprises a tracking wireless network.

Preferably, the tag readers and the tags are battery-powered.

Preferably, the wireless network comprises an ad-hoc, multi-nodewireless network.

Preferably, the wireless network comprises a wireless sensor network.

As a further aspect of the invention, there is provided a method ofincreasing probability of detection of rapidly moving clusters of mobilenodes in a wireless network, the method comprising:

-   -   organizing nodes in the wireless network into a hierarchy of        tiers comprising:        -   a first tier comprising a plurality of tagged personal            devices;        -   a second tier comprising at least one tagged vehicle device;            and        -   a third tier comprising at least one tagged infrastructure            device;    -   wherein the plurality of tagged personal devices connect to a        nearest tagged vehicle device among the at least one tagged        vehicle device, and each one of the at least one tagged vehicle        device connect to a nearest infrastructure device among the at        least one tagged infrastructure device;    -   exchanging data messages between the nearest tagged vehicle        device and the nearest tagged infrastructure device, where the        messages comprise data in association with the plurality of        tagged personal devices.

Preferably, the wireless network is a batter-powered mesh network.

BRIEF DESCRIPTION OF THE DRAWINGS Detailed Description of the PreferredEmbodiment

Novel methods, devices and systems for Tracking of and Communicationwith Mobile Terminals using a Battery-Powered Wireless NetworkInfrastructure will be described hereinafter. Although the invention isdescribed in terms of specific illustrative embodiments, it is to beunderstood that the embodiments described herein are by way of exampleonly and that the scope of the invention is not intended to be limitedthereby.

Being directed to a network technology comprising different aspects,these different aspects shall now be described separately.

The system and method of the present invention are most preferablyembodied in a wireless network system and are generally mostadvantageously applied to networks requiring low energy consumption suchas sensor networks. However, the system and method of the presentinvention may be applied to other fields such as, but not limited to,personal, vehicle and asset tracking and mobile communications inunderground mines, navy vessels, and military persistent surveillancefield deployments; the present invention is not so limited.

The network system of the present invention generally consists of aplurality of substantially structurally identical wireless nodes.Identical nodes enable more efficient network deployment because anynode can be installed at any location without affecting networkfunctioning. Moreover, malfunctioning or damaged nodes can be replacedeasily and on short notice.

In one embodiment of the invention, communication occurs between aninfrastructure node and a mobile node. Each infrastructure node has itsown time and frequency synchronization.

A major distinction of the present invention with respect to the priorart is that a node is not provided with multiple antennas andtransceivers. Each node of the present invention is provided with asingle antenna and a single transceiver. The ability to be synchronizedwith more than one clock and with more than one frequency hoppingsequence is provided by the proprietary software embedded in eachwireless node.

Compared to previous art, all the roles in this embodiment have routingcapabilities regardless of how frequently they transmit beacons. Therole of each node in the network will adapt according to the localradio-frequency (“RF”) environment, node density, throughputrequirements, energy consumption, and required routing. Beacontransmission is globally reduced to a minimum in this embodiment of abeacon-based mesh network.

The process is enabled by the transmission of beacons by theinfrastructure nodes. The mobile nodes receive the different beacons andconnect to the closest infrastructure node.

The features of the present invention which are believed to be novel areset forth with particularity in the appended claims.

As a first aspect of the invention, there is provided a method of energymanagement of tag readers in a wireless network.

According to the preferred embodiment, the wireless network consists ofan ad hoc battery-powered mesh network mounted in an underground areasuch as mines or in a confined area such as navy vessels. Since physicalaccess to such areas is most of the time very difficult and cableinstallation is sometimes impossible, there is a need for a wirelessnetwork that would be battery-powered and that would minimize humanintervention. The human intervention is minimized if the network is selfhealing and if the power battery of the tag readers (infrastructurenodes) can last the longest time possible.

The first purpose of the conceived wireless network in accordance withthe preferred embodiment is to track personal and machinery insideunderground mines.

Infrastructure nodes (tag readers) are mounted in different zones of theunderground mine or navy vessel in order to track presence of personaland machinery. Personal and machinery are tagged with battery-powered ormachine-powered tags which continuously communicate with the nearest tagreader. The process of communication between the tag and tag reader is anovel aspect of the present invention, since it is conceived to minimizeenergy consumption of the tag reader.

The communication protocol between tags and tag readers can be describedas follows:

Activities of the Tag Reader (Infrastructure Node):

The INFRASTRUCTURE NODE IS IN DEEP SLEEP MODE EXCEPT WHEN EXECUTING THEFOLLOWING PROCESSES:

1—PERIODIC TRANSMISSION OF BEACON:

-   -   NODE ID (UNIQUE FOR EACH INFRASTRUCTURE NODE)    -   CHANNEL PARAMETERS (UNIQUE FOR EACH INFRASTRUCTURE NODE)    -   NEXT TIME SLOT WHEN THE RECEIVER IS ON FOR RANDOM ACCESS TO        INITIATE CONNECTION (UNIQUE FOR EACH INFRASTRUCTURE NODE)    -   ON-DEMAND ALLOCATION OF TIME SLOTS TO SPECIFIC MOBILE NODES FOR        BI-DIRECTIONAL COMMUNICATIONS (I.E. CSMA IS NOT USED ONCE A        CONNECTION IS ESTABLISHED)    -   BACKHAUL NETWORKING OPTION ON/OFF    -   TRACKING CAPABILITY OPTION ON/OFF    -   SIZE OF TRACKING CELL/ZONE (E.G. SMALL, MEDIUM, LARGE)

Example

-   -   A beacon is sent once per frame in a pre-defined time slot. A        frame is a collection of 50 pre-defined time slots, each lasting        13 ms. The time the beacon is transmitted defines the time        synchronization for that infrastructure node.    -   Message is 64 bits:    -   Bits [0-4]: Msg Type (MSG_BEACON=0)    -   Bits [5-20]: Infrastructure node ID    -   Bits [21-52]: Frequency Hopping Random Seed    -   Bits [53-56]: Beacon Time Offset    -   Bits [57-58]: Tracking Node Type (Tracking OFF (0), Tracking ON        with small (1), medium (2), large coverage areas (3))    -   Bits [59]: Backhaul communication ON/OFF    -   Bits [60-63]: Reserved for other services    -   The frequency hopping random seed is unique per infrastructure        node. It defines the channel that will be used for communication        for each time slot.

2—PERMANENT CONNECTIONS WITH NEIGHBORING INFRASTRUCTURE NODES FORBACKHAUL COMMUNICATIONS TO CENTRAL SERVER (USING PRIOR ART LOW POWERSTAR OR MESH NETWORKING TECHNOLOGIES)

3—RECEPTION OF 1) CONNECTION AND 2) REQUEST_FOR_COMMUNICATION_TIMESLOTSMESSAGES(*) FROM MOBILE NODES ON RANDOM ACCESS CHANNEL

Example

-   -   Reception of connection message must be received within 1 ms of        beginning of allocated time slot.    -   The connection message has 64 bits.    -   Bits [0-4]: Msg Type (MSG_CONNECTION=1)    -   Bits [5-20]: Mobile node ID    -   Bits [21-36]: Infrastructure node ID    -   Bits [37-41]: Device Type (MOBILE_WITH_TRACKING (0),        MOBILE_WITHOUT_TRACKING (1), LEAF (2), ROUTER (3))    -   Bits [42-49]: Application bits (for example, engine and ignition        state)    -   Bits [50-53]: Tracking error function for server-level        intelligence    -   Bits [54-63]: Reserved    -   The Request for communication time slots message has 64 bits:    -   Bits [0-4]: Msg Type (REQUEST_FOR_COMMUNICATION_TIME_SLOTS=2)    -   Bits [5-20]: Mobile node ID    -   Bits [21-36]: Infrastructure node ID    -   Bits [37-52]: Number of requested time slots    -   The mobile requests for time slot when it needs to send a        message to the infrastructure node.

4—ON-DEMAND CONNECTION WITH MOBILE NODES FOR TWO-WAY COMMUNICATIONS(E.G. PERIODIC HEARTBEAT, SENSOR DATA, ACKNOWLEDGMENT, CONFIGURATIONPARAMETERS)

Example

-   -   When the infrastructure node receives a connection attempt from        a mobile node, it registers the node. If the node is of type        MOBILE_WITH_TRACKING, it will guarantee the transmission of the        tracking message to the server. From then on, the infrastructure        node will allocate specific time slots for communication as        requested by the mobile node or needed by it.    -   When the mobile node requests for communication time slots, the        infrastructure node sends an allocation message in another        pre-defined time slot which defines the communication time        slots, in which the mobile node may send information.    -   When the infrastructure node wants to send a message, it sends        an allocation message which specifies the time slot of        communication.

5—EVENT-DRIVEN TRANSMISSION OF MOBILE NODE CONNECT/DISCONNECTMESSAGE(**) (BASED ON PRESENCE/ABSENCE OF PERIODIC TAG HEARTBEAT) TOCENTRAL SERVER

Example

-   -   The mobile node sends a heartbeat every minute to the        infrastructure node. If 3 are not received in a row, it is        considered not connected. At that point, a disconnection message        is sent to the server with a time stamp.

Hardware Options of the Infrastructure Nodes:

Hardware Component Options:

-   -   Low Power Microcontroller options: Texas Instrument MSP430F1612,        Jennic JN5139    -   Low Power Transceiver options: Semtech XE1203, Chipcon CC2420    -   Primary Battery options: Tadiran lithium thionyl chloride        primary batteries    -   Energy Harvesting options: Nanosolar solar cells combined with a        lithium-ion rechargeable battery

Integrated Hardware Platform Option #1: All processes mentionedhereinabove related to the communications with infrastructure nodes areimplemented using the same microcontroller and transceiver. Power issupplied by a primary battery or an energy harvesting mechanism.

Integrated Hardware Platform Option #2: All processes mentionedhereinabove related to communications with mobile nodes are implementedon one microcontroller/transceiver pair, and all processes related tobackhaul communications to a central server are implemented on a 2ndmicrocontroller/transceiver pair. Communications between processes ontwo microcontrollers is done via SPI, UART or RS-232. Power is suppliedby a primary battery or an energy harvesting mechanism.

Activities of the Tags (Mobile Nodes):

MOBILE NODE EXECUTES THE FOLLOWING PROCESSES:

1—CONTINUOUSLY LISTENS FOR INFRASTRUCTURE NODE BEACONS

Example

Use 8 different beacon frequencies that are common for allinfrastructure nodes. These frequencies are connection frequencies. Themobile node listens to one of them at a time for a duration that isequal to the period of these connection frequencies. For instance, theperiod could be is 19 frames with 50 time slots of 13 ms=12.350 seconds.

2—USES THE BEACON TO EVALUATE THE RSSI, TOF OR OTHER RF LINK PARAMETERSWITH INFRASTRUCTURE NODES WHICH HAVE TRACKING ON

Example

-   -   The node measures the RSSI of the nodes around it. If one of        them has not been evaluated recently and its RSSI is stronger        than a threshold or is the strongest, it will decide to        connection to it for further evaluation.

3—ATTEMPTS TO DETERMINE THE NEAREST INFRASTRUCTURE NODE BY CONSIDERINGINSTANTANEOUS AND/OR HISTORICAL RF LINK DATA (WHICH HAS TRACKING ON ANDWHOSE RF LINK PARAMETERS MEET THE RF SIGNAL STRENGTH OR TIME OF FLIGHTREQUIREMENTS SPECIFIED IN ITS BEACON)

Example

-   -   The mobile node will make further evaluation of the        infrastructure node while monitoring the other infrastructure        nodes around it. If the RSSI signature meets the requirements of        an infrastructure node that is the closest, it will decide to        connect to it.

4—TRANSMITS 1) CONNECTION OR 2) REQUEST_FOR_COMMUNICATION MESSAGES (*)ON THE RANDOM ACCESS CHANNEL OF THE SELECTED NEAREST INFRASTRUCTURE NODE(PREFERABLY) OR ANY OTHER INFRASTRUCTURE NODE WITH:

CONNECTION MESSAGE:

-   -   MOBILE NODE ID    -   INFRASTRUCTURE NODE ID    -   NEAREST INFRASTRUCTURE NODE ESTIMATION ERROR FUNCTION PARAMETERS    -   SHORT APPLICATION PAYLOAD (OPTIONAL, FOR INSTANCE MESSAGE (**))

REQUEST FOR COMMUNICATION TIME SLOT MESSAGE:

-   -   MOBILE NODE ID    -   INFRASTRUCTURE NODE ID    -   NUMBER OF REQUESTED TIME SLOTS

Example

-   -   While it is connected to it, it will monitor its RSSI signature        in order to determine if it is going out of range of the        coverage area which defined by the Tracking Node Type. If it        does, it will attempt to send a disconnection message. Then it        will go back to step 1.    -   The connection message has 64 bits.    -   Bits [0-4]: Msg Type (MSG_CONNECTION=1)    -   Bits [5-20]: Mobile node ID    -   Bits [21-36]: Infrastructure node ID    -   Bits [37-41]: Device Type (MOBILE_WITH_TRACKING (0),        MOBILE_WITHOUT_TRACKING (1), LEAF (2), ROUTER (3))    -   Bits [42-49]: Application bits (for example, engine and ignition        state)    -   Bits [50-53]: Tracking error function for server-level        intelligence    -   Bits [54-63]: Reserved    -   The Request for communication time slots message has 64 bits:    -   Bits [0-4]: Msg Type (REQUEST_FOR_COMMUNICATION_TIME_SLOTS 2)    -   Bits [5-20]: Mobile node ID    -   Bits [21-36]: Infrastructure node ID    -   Bits [37-52]: Number of requested time slots

5—ESTABLISHES TWO-WAY CONNECTION WITH THE SELECTED NEARESTINFRASTRUCTURE NODE (PREFERABLY) OR ANY OTHER INFRASTRUCTURE NODE ANDEXCHANGES PERIODIC HEARTBEAT

Example

-   -   The connection is done with the connection message as in 4.    -   Definition of how communication are requested is done in the        infrastructure section. Here's a repetition:    -   The Request for communication time slots message has 64 bits:    -   Bits [0-4]: Msg Type (REQUEST_FOR_COMMUNICATION_TIME_SLOTS 2)    -   Bits [5-20]: Mobile node ID    -   Bits [21-36]: Infrastructure node ID    -   Bits [37-52]: Number of requested time slots    -   The mobile requests for time slot when it needs to send a        message to the infrastructure node.    -   When the mobile node requests for communication time slots, the        infrastructure node sends an allocation message in another        pre-defined time slot which defines the communication time        slots, in which the mobile node may send information.    -   When the infrastructure node wants to send a message, it sends        an allocation message which specifies the time slot of        communication.

6—INFRASTRUCTURE NODE IS RESPONSIBLE FOR THE GUARANTEED DELIVERY OF THEMOBILE NODE MESSAGES TO THE CENTRAL SERVER

Example

-   -   The infrastructure node will send through the backhaul a        tracking message of 128 bits.    -   Bits [0-4]: Msg Type (APPLICATION_PAYLOAD=3)    -   Bits [5-20]: Infrastructure node ID    -   Bits [21-36]: Target ID (in this case SERVER_ID)    -   Bits [37-47]: Reserved    -   Bits [48-55]: Application Msg Type (TRACKING=0)    -   Bits [56-71]: Mobile ID    -   Bits [72-103] Time of Occurrence    -   Bits [104-111]: Tracking Error function parameters    -   Bits [112-127]: Reserved    -   An acknowledge will be received from the server if it was        received.

Hardware Options of the Mobile Nodes (Tags):

Hardware Components Options:

-   -   Low Power Microcontroller options: Texas Instrument MSP430F1612,        Jennic JN5139    -   Low Power Transceiver options: Semtech XE1203, Chipcon CC2420    -   Primary Battery options: Tadiran lithium thionyl chloride        primary batteries    -   Energy Harvesting options: Nanosolar solar cells combined with a        lithium-ion rechargeable battery    -   Rechargeable Battery options: Lithium-ion battery recharged        frequently as part of normal operations (e.g. miner cap lamp,        first responder mobile terminal)    -   Line power options: Vehicle or machinery power bus

Hardware Platform Option #1: All processes mentioned hereinabove relatedto the mobile nodes are implemented using the same microcontroller andtransceiver. Power is supplied by a rechargeable battery, line power, aprimary battery or an energy harvesting mechanism.

From a higher level abstract, the activities of the reader andtag-reader can be illustrated as follow:

1. Tag-reader in deep sleep mode periodically wakes up to send asynchronization message every X seconds;

2. Tag is able to determine the nearest tag-reader by listening to thesynchronization messages of tag-readers:

-   -   a. In the preferred embodiment based on Frequency Hopping Spread        Spectrum (FHSS), the tag measures the Received Signal Strength        (RSSI) by listening to the synchronization message.    -   b. In an alternative embodiment based on Chirp Spread Spectrum        (CSS), the tag measure Round-Trip Time-Of-Flight (RTTOF) by        listening to the synchronization message.

3. Tag listens until it captures the synchronization message required toinitiate bi-directional communications with the tag-reader:

-   -   a. In the preferred embodiment based on FHSS, the        synchronization message has the random seed of the communication        channels (i.e. frequencies and time slots). Its time of        reception gives the asynchronous time base of the reader.

4. In order to maximize its sleep time, the tag-reader allocatesspecific time slots for communications with the tag. One time slot isalways allocated for tracking messages. This time slot will be referredto as the “random-access time slot”:

-   -   a. In the preferred embodiment based on FHSS, the tag reader        allocates both frequency channels and time slots for        communications

5. After interpreting the RSSI and/or RTTOF measurements, the tagdecides whether to send a tracking message to the reader in therandom-access time slot.

-   -   a. In the preferred embodiment, the interpretation is made with        a log of previous RSSI measurements, which can be made at        different frequencies or channels, from surrounding readers. The        tracking message contains the time of occurrence of tracking,        the network address of the tag and qualitative RSSI information.

6. Tag-reader forwards the tracking message to the battery-poweredwireless mesh network router for transmission to a central server.

As a further aspect of the invention, there is provided a method toincrease probability of detection of rapidly moving clusters of mobilenodes in a battery-powered mesh network.

Hybrid Infrastructure-Mobile Node on Vehicle to Track Clusters of MobileTags Moving at High Speed:

INFRASTRUCTURE NODE “PART/PORTION” EXECUTES THE FOLLOWING PROCESSES:

1B—PERIODIC TRANSMISSION OF BEACON:

-   -   NODE ID (UNIQUE FOR EACH INFRASTRUCTURE NODE)    -   CHANNEL PARAMETERS (UNIQUE FOR EACH INFRASTRUCTURE NODE)    -   NEXT TIME SLOT WHEN THE RECEIVER IS ON FOR RANDOM ACCESS TO        INITIATE CONNECTION (UNIQUE FOR EACH INFRASTRUCTURE NODE)    -   ON-DEMAND ALLOCATION OF TIME SLOTS TO SPECIFIC MOBILE NODES FOR        BI-DIRECTIONAL COMMUNICATIONS    -   BACKHAUL NETWORKING OPTION ON/OFF    -   TRACKING CAPABILITY OPTION ON/OFF    -   RF SIGNAL STRENGTH OR TIME OF FLIGHT DEFINING SIZE OF TRACKING        CELL/ZONE

2B—RECEPTION OF MESSAGES(*) FROM MOBILE NODES ON RANDOM ACCESS CHANNEL

3B—ON-DEMAND CONNECTION WITH MOBILE NODES FOR TWO-WAY COMMUNICATIONS(E.G. PERIODIC HEARTBEAT, SENSOR DATA, ACKNOWLEDGMENT, CONFIGURATIONPARAMETERS)

4B—EVENT-DRIVEN TRANSMISSION OF MOBILE NODE CONNECT/DISCONNECT MESSAGE(**) (BASED ON PRESENCE/ABSENCE OF PERIODIC TAG HEARTBEAT) TO CENTRALSERVER VIA WIRED PORT (E.G. SPI. RS-232) TO MOBILE NODE “PART/PORTION”OF HYBRID DEVICE

MOBILE NODE “PART/PORTION” EXECUTES THE FOLLOWING PROCESSES:

1B—CONTINUOUSLY LISTENS FOR INFRASTRUCTURE NODE BEACONS

2B—USES THE BEACON TO EVALUATE THE RSSI, TOF OR OTHER RF LINK PARAMETERSWITH INFRASTRUCTURE NODES WHICH HAVE BACKHAUL NETWORKING AND TRACKING ON

3B—SELECTS THE NEAREST INFRASTRUCTURE NODE (WHICH HAS BACKHAULNETWORKING AND TRACKING ON AND WHOSE RF LINK PARAMETERS MEET THE MINIMUMRF THRESHOLDS SPECIFIED IN ITS BEACON)

4B—RECEPTION OF MESSAGES(**) FROM INFRASTRUCTURE NODE “PART/PORTION” OFHYBRID DEVICE VIA WIRED PORT (E.G. SPI. RS-232) 5B-TRANSMITSMESSAGES(*)+(**) ON THE RANDOM ACCESS CHANNEL OF THE SELECTED NEARESTINFRASTRUCTURE NODE (PREFERABLY) OR ANY OTHER INFRASTRUCTURE NODE WITH:

6B—ESTABLISHES TWO-WAY CONNECTION WITH THE SELECTED NEARESTINFRASTRUCTURE NODE (PREFERABLY) OR ANY OTHER INFRASTRUCTURE NODE ANDEXCHANGES PERIODIC HEARTBEAT;

Hardware Options of the Hybrid Nodes (Tags):

Hardware Platform Option #1: All processes in Flow Chart #3 areimplemented using the same microcontroller and transceiver. Power issupplied by a rechargeable battery, line power, a primary battery or anenergy harvesting mechanism.

Hardware Platform Option #2: All processes related to the mobile node“part/portion” are implemented on the same hardware platform as a normalmobile node, and all processes related to the infrastructure node“part/portion” are implemented on the same hardware platform as a normalinfrastructure node. Both hardware platforms are inter-connected by awired SPI, UART or RS-232 port. Power is supplied by a rechargeablebattery, line power, a primary battery or an energy harvestingmechanism.

While illustrative and presently preferred embodiments of the inventionhave been described in detail hereinabove, it is to be understood thatthe inventive concepts may be otherwise variously embodied and employedand that the appended claims are intended to be construed to includesuch variations except insofar as limited by the prior art.

1. A method of reducing energy consumption of tag readers in a wirelessnetwork, the method comprising: a) turning a transmitter and a receiverof said tag reader to a power-off state; b) powering-on the transmitterof said tag reader for a limited transmission time frame; c) during saidtransmission time frame, transmitting a beacon message comprising anidentifier of said tag reader, channel characteristics of said tagreader and a powering-on schedule of the receiver of said tag reader,for allowing tags in the network to communicate with said tag reader,where said tags are almost continuously in a power-on state; c)powering-on the receiver of said tag reader during a limited receptiontime frame in accordance with said schedule, for enabling said receiverto receive messages transmitted by said tags in the network if required;d) repeating steps a) to d) periodically.
 2. The method as claimed inclaim 1, wherein said wireless network comprises a tracking wirelessnetwork.
 3. The method as claimed in claim 2, wherein said tag readersand said tags are battery-powered.
 4. The method as claimed in claim 1,wherein said wireless network comprises an ad-hoc, multi-node wirelessnetwork.
 5. The method as claimed in claim 1, wherein said wirelessnetwork comprises a wireless sensor network.
 6. A tag reader in awireless network comprising: a transmitter; a receiver; a processingunit configured to turn a transmitter and a receiver of said tag readerto a power-off state, to power-on the transmitter of said tag reader fora limited transmission time frame, to transmit, during said transmissiontime frame, a beacon message comprising an identifier of said tag,reader, channel characteristics of said tag reader and a powering-onschedule of the receiver of said tag reader for allowing tags in thenetwork to communicate with said tag reader, and to power-on thereceiver of said tag reader during a limited reception time frame inaccordance with said schedule for enabling said receiver to receivemessages transmitted by tags in the network if required.
 7. The tagreader as claimed in claim 6, wherein said wireless network comprises atracking wireless network.
 8. The tag reader as claimed in claim 7,wherein said tag readers and said tags are battery-powered.
 9. The tagreader as claimed in claim 6, wherein said wireless network comprises anad-hoc, multi-node wireless network.
 10. The tag reader as claimed inclaim 6, wherein said wireless network comprises a wireless sensornetwork.
 11. A wireless network comprising a plurality of tags and aplurality of tag readers, where tag readers are configured to becontinuously in a power-off state except during prescheduled receptionand transmission time frames, and where tags are configured to be almostcontinuously in a power-on state, where said tags and tag readersexchange messages therebetween in order for each tag to be connected toone tag reader in the network.
 12. The wireless network as claimed inclaim 11, wherein said wireless network is a tracking wireless network.13. The wireless network as claimed in claim 12, wherein said tagreaders and said tags are battery-powered.
 14. The wireless network asclaimed in claim 11, wherein said wireless network comprises an ad-hoc,multi-node wireless network.
 15. The wireless network as claimed inclaim 11, wherein said wireless network comprises a wireless sensornetwork.
 16. A computer-readable medium containing instructions forcontrolling at least one processor to perform a method of reducingenergy consumption in an immobile node in a wireless network, the methodcomprising: a) turning a transmitter and a receiver of said tag readerto a power-off state; b) powering-on the transmitter of said tag readerfor a limited transmission time frame; c) during said transmission timeframe, transmitting a beacon message comprising an identifier of saidtag reader, channel characteristics of said tag reader and a powering-onschedule of the receiver of said tag reader, for allowing tags in thenetwork to communicate with said tag reader, where said tags are almostcontinuously in a power-on state; c) powering-on the receiver of saidtag reader during a limited reception time frame in accordance with saidschedule, for enabling said receiver to receive messages transmitted bysaid tags in the network if required; d) repeating steps a) to d)periodically.
 17. A method of increasing probability of detection ofrapidly moving clusters of mobile nodes in a wireless network, themethod comprising: organizing nodes in said wireless network into ahierarchy of tiers comprising: a first tier comprising a plurality oftagged personal devices; a second tier comprising at least one taggedvehicle device; and a third tier comprising at least one taggedinfrastructure device; wherein said plurality of tagged personal devicesconnect to a nearest tagged vehicle device among said at least onetagged vehicle device, and each one of said at least one tagged vehicledevice connect to a nearest infrastructure device among said at leastone tagged infrastructure device; exchanging data messages between saidnearest tagged vehicle device and said nearest tagged infrastructuredevice, where said messages comprise data in association with saidplurality of tagged personal devices.
 18. A method as claimed in claim17, wherein said wireless network is a battery-powered mesh network.